The business community has long supported the idea of immigration reform — particularly the high-tech sector and the construction industry, which badly need the workers.

What they don’t support are some of the specifics leaking out on a new immigration reform proposal expected Tuesday from the Gang of Eight.

Now, companies and trade groups — that have been pressuring the key Senate negotiators — are preparing to unleash their lobbying forces broadly on Capitol Hill in hopes of securing changes to the package.

And that could spell trouble for the bill since any significant change to even a single element could scuttle the delicately reached bargain, leaving final passage of a comprehensive immigration reform bill in serious jeopardy.

“There are a host of different interests who will want to go to the other 92 senators,” said veteran lobbyist Tony Podesta, who represents several clients on the issue. “I think the immigration groups, high-tech community, there are lots of interests that are implicated, the agriculture industry, lots of concerns and interests that will matter a lot to people, to companies that rely a lot on Indian technology consulting companies.”

When the bill is unveiled, the eight key negotiators are expected to have signed off on the plan. Sen. Marco Rubio (R-Fla.) already gave the deal a full-throat endorsement on Sunday’s talk shows.

The pressure campaigns that have been going on behind the scenes during negotiations will go public with a growing number of companies and industries over specific provisions in the Senate legislation.

Case in point: Silicon Valley.

For the past several years, tech companies have pushed lawmakers to overhaul the H-1B visa program, arguing that there aren’t enough high-skilled American workers to fill positions and that they don’t even have enough visas to bring in foreign workers.

Today, H-1B visas are capped at 65,000 annually, with 20,000 more for those with advanced degrees. Earlier this month, the Homeland Security Department announced it received more visa requests than available for the 2014 fiscal year after just a week of accepting applications.

Several tech lobbyists said they think the Senate Gang of Eight’s plan won’t increase the number of H-1B visas by nearly enough. Final details of the plan haven’t been made public, yet.

“Tech companies have been the primary driver of reinforcing the need for immigration reform, and now, it looks like their concerns are totally being thrown overboard,” one tech lobbyist said.

The Senate package is expected to contain a provision that will not allow companies to displace an American worker in the same region and occupation unless the entire number of American workers in that occupation has remained the same or increased. That provision could have a big impact on large companies like IBM, Deloitte and Accenture.

And Indian companies like Infosys, TCS and Wipro, heavy users of H-1Bs for their U.S. workforce, will have to pay big fees under a new fee formula.

Tech lobbyists said staff familiar with the talks have said the plan requires companies that have 30 percent of their workforce in foreign workers to pay a higher wage and those that employ 50 percent of their workers by the visa holders an even higher wage.

Companies like Microsoft, Intel, IBM, Expedia and education groups are also doing meetings on Capitol Hill with Senate offices and have plans to set up caucus meetings in the next few weeks to push for more investment in science, technology, engineering and math — known as STEM.

James Brett, head of The New England Council, which consists of corporations, hospitals and other groups, said that not including a STEM fund in immigration reform is short-sighted.

“If we do not have a longer-term solution to the shortage of high-skilled STEM workers by developing that domestic pipeline, we are going to be back at this,” said Brett, who has been personally making the case to the New England delegations to get this added to the bill.

One coalition, inSPIRE STEM USA, also has plans to take out print advertisements next week.

The restaurant industry is also getting in on the action.

The National Restaurant Association is talking actively with its allies over concerns about employment verification.

Early drafts of the legislative language included two titles devoted to labor. Unlike the temporary guest worker program, which is optional, employment verification would be mandatory. The restaurant group fears the provisions could place an unfair burden on them in the hiring process.

Meanwhile, the construction industry is lobbying and having its members call lawmakers over a deal for future low-skilled temporary workers.

Associated Builders and Contractors’ Geoff Burr is leading the charge to make changes to what the group thinksis an inadequate number of visas being allocated to the construction industry.

Nearly 30 trade groups and companies wrote a letter earlier this week to House leaders raising their concerns about the size of the temporary guest worker program.

“Regardless of the fact that no one has been able to articulate why our industry requires special treatment, it’s incomprehensible to craft a program that allocates 15,000 visas per year to an industry that employs over 6 million workers and accounts for more than 5 percent of our economy,” Burr said.

“This guest worker program needs to respond to labor market demands in times of both high and low unemployment, and the program proposed here fails to achieve that goal.”